U.S. patent application number 15/864540 was filed with the patent office on 2018-07-12 for lighting device using light-emitting elements as light source.
This patent application is currently assigned to PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO., LTD.. The applicant listed for this patent is PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO., LTD.. Invention is credited to Ryuji HOTTA, Masae SUZUKI, Masaki TADA.
Application Number | 20180195688 15/864540 |
Document ID | / |
Family ID | 62781818 |
Filed Date | 2018-07-12 |
United States Patent
Application |
20180195688 |
Kind Code |
A1 |
SUZUKI; Masae ; et
al. |
July 12, 2018 |
LIGHTING DEVICE USING LIGHT-EMITTING ELEMENTS AS LIGHT SOURCE
Abstract
A lighting device includes a light source and first and second
reflection surfaces. The first reflection surface reflects source
light from the light source, and projects first light on first and
second regions on an illuminated surface. The second region is
closer to the lighting device than the first region. The second
reflection surface is tinted in a prescribed color, and reflects
secondary and higher-order reflection light of the source light,
and projects second light on the second region. An absolute value
of a difference between correlated color temperatures of the first
light projected on the first region and of mixed light of the first
and second lights projected on the second region is smaller than an
absolute value of a difference between correlated color
temperatures of the first light projected on the first region and
of the first light projected on the second region.
Inventors: |
SUZUKI; Masae; (Saitama,
JP) ; HOTTA; Ryuji; (Tokyo, JP) ; TADA;
Masaki; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO., LTD. |
Osaka |
|
JP |
|
|
Assignee: |
PANASONIC INTELLECTUAL PROPERTY
MANAGEMENT CO., LTD.
Osaka
JP
|
Family ID: |
62781818 |
Appl. No.: |
15/864540 |
Filed: |
January 8, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F21Y 2115/10 20160801;
F21V 13/10 20130101; F21V 11/16 20130101; F21V 3/00 20130101; F21V
7/06 20130101; A47F 3/001 20130101; F21Y 2113/10 20160801; F21V
7/22 20130101; F21Y 2103/10 20160801 |
International
Class: |
F21V 7/22 20060101
F21V007/22; F21V 11/16 20060101 F21V011/16; F21V 3/00 20060101
F21V003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 10, 2017 |
JP |
2017-001632 |
Claims
1. A lighting device comprising: a light source including at least
two types of light-emitting elements arranged in one direction, the
at least two types of light-emitting elements having correlated
color temperatures of emitted light being different from each
other; a first reflection surface configured to reflect source
light emitted from the light source, and project first light that
is the reflected source light, on first and second regions on a
surface illuminated by the lighting device, the second region being
located closer to the lighting device than the first region; and a
second reflection surface tinted in a prescribed color and
configured to reflect secondary and higher-order reflection light
of the source light, and project second light that is the reflected
secondary and higher-order reflection light, on the second region,
wherein an absolute value of a difference between a correlated
color temperature of the first light projected on the first region
and a correlated color temperature of mixed light of the first and
second lights projected on the second region, is smaller than an
absolute value of a difference between the correlated color
temperature of the first light projected on the first region and a
correlated color temperature of the first light projected on the
second region.
2. The lighting device according to claim 1, wherein the correlated
color temperature of the first light projected on the first region
is lower than the correlated color temperature of the first light
projected on the second region, and an average value of the
correlated color temperature of the second light is lower than an
average value of the correlated color temperature of the first
light.
3. The lighting device according to claim 2, wherein the at least
two types of light-emitting elements include a first light-emitting
element and a second light-emitting element, the first and second
light-emitting elements have the correlated color temperatures of
the emitted light being different from each other, the lighting
device includes a control unit configured to control light outputs
from the first and second light-emitting elements, the control unit
makes a correlated color temperature of the source light variable
in a prescribed range, a median value of which is a first
correlated color temperature, by changing light output ratio
between the first and second light-emitting elements, and when the
correlated color temperature of the source light is equal to the
first correlated color temperature, the correlated color
temperature of the first light projected on the first region is
lower than the correlated color temperature of the first light
projected on the second region, and the average value of the
correlated color temperature of the second light is lower than the
average value of the correlated color temperature of the first
light.
4. The lighting device according to claim 1, wherein the correlated
color temperature of the first light projected on the first region
is higher than the correlated color temperature of the first light
projected on the second region, and an average value of the
correlated color temperature of the second light is higher than an
average value of the correlated color temperature of the first
light.
5. The lighting device according to claim 4, wherein the at least
two types of light-emitting elements include a first light-emitting
element and a second light-emitting element, the first and second
light-emitting elements have the correlated color temperatures of
the emitted light being different from each other, the lighting
device includes a control unit configured to control light outputs
from the first and second light-emitting elements, the control unit
makes a correlated color temperature of the source light variable
in a prescribed range, a median value of which is a first
correlated color temperature, by changing light output ratio
between the first and second light-emitting elements, and when the
correlated color temperature of the source light is equal to the
first correlated color temperature, the correlated color
temperature of the first light projected on the first region is
higher than the correlated color temperature of the first light
projected on the second region, and the average value of the
correlated color temperature of the second light is higher than the
average value of the correlated color temperature of the first
light.
6. The lighting device according to claim 1, further comprising: a
light shielding plate configured to suppress projection of the
source light on the first and second regions without being
reflected from the first reflection surface, wherein the second
reflection surface is provided to the light shielding plate.
7. The lighting device according to claim 1, further comprising: a
diffuser panel configured to diffuse light incident from the first
reflection surface and project the diffused light toward the first
and second regions.
Description
BACKGROUND
Technical Field
[0001] This disclosure relates to a lighting device which uses
light-emitting elements such as light-emitting diodes (LEDs) as its
light source.
Background Art
[0002] There is a lighting device that can change the color of
illumination light by using multiple types of light-emitting
elements that provide different emission colors from one another,
and adjusting outputs from the respective light-emitting elements.
Japanese Unexamined Patent Application Publication No. 2014-120396
discloses a related art.
[0003] However, the lighting device using multiple types of the
light-emitting elements which have correlated color temperatures of
emitted light being different from each other may cause color
unevenness on an illuminated surface due to factors such as
variations in light distribution characteristics, optical axis
deviations, displacements of mounting positions, and the like among
the light-emitting elements.
SUMMARY
[0004] This disclosure has been made in view of the problem of the
related art. An object of this disclosure is to efficiently
suppress the color unevenness on the illuminated surface.
[0005] A lighting device according to an aspect of this disclosure
includes: a light source in which two or more types of
light-emitting elements that have correlated color temperatures of
emitted light being different from each other are arranged in one
direction; a first reflection surface; and a second reflection
surface. The first reflection surface reflects source light emitted
from the light source, and projects first light that is the
reflected source light, on first and second regions on a surface
illuminated by the lighting device, the second region being located
closer to the lighting device than the first region. The second
reflection surface reflects secondary and higher-order reflection
light of the source light, and projects second light that is the
reflected secondary and higher-order reflection light, on the
second region. The second reflection surface is tinted in a
prescribed color. An absolute value of a difference between a
correlated color temperature of the first light projected on the
first region and a correlated color temperature of mixed light of
the first and second lights projected on the second region is
smaller than an absolute value of a difference between the
correlated color temperature of the first light projected on the
first region and a correlated color temperature of the first light
projected on the second region.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] The figures depict one or more implementations in accordance
with the present teaching, by way of example only, not by way of
limitations. In the figures, like reference numerals refer to the
same or similar elements.
[0007] FIG. 1 is a layout drawing of a lighting device according to
an embodiment of this disclosure.
[0008] FIG. 2 is a cross-sectional view taken along the A-A line in
FIG. 1.
[0009] FIG. 3 is a diagram showing a projection region of first
light from the lighting device according to the embodiment.
[0010] FIG. 4 is a diagram showing a projection region of second
light from the lighting device according to the embodiment.
[0011] FIG. 5 is a cross-sectional view of the lighting device
according to the embodiment.
[0012] FIG. 6 is a layout drawing of LEDs in a light source
according to the embodiment.
DETAILED DESCRIPTION
[0013] Embodiments of the present disclosure will be described
below with reference to the drawings. It is to be noted that the
terms indicating directions such as "above", "below", "front", and
"back" are defined for the sake of the illustration of positional
relations of components and are not intended to restrict conditions
such as orientations to attach the components in an actual
device.
[0014] As shown in FIGS. 1 to 4, a lighting device 1 can be
installed in a showcase 10 which is used, for example, in a
gallery, a museum, and the like. The showcase 10 includes a display
table 11, a top wall 12, a back wall 13, a front wall 14, and right
and left side walls 15, and defines a display space S inside. The
front wall 14 is provided with a transparent panel 14a which makes
the display space S visible from a position in front of the
showcase 10. An upper shield wall 14b and a lower shield wall 14c
are provided above and below the transparent panel 14a. A showpiece
such as a painting and a sculpture is displayed by being hung on a
front face 13a of the back wall 13 or being placed on an upper face
11a of the display table 11.
[0015] As shown in FIG. 1, for example, multiple lighting devices 1
are installed substantially across the entire length of the display
space S. The lighting devices 1 have an elongated shape and are
arranged to extend at a position in front of the back wall 13
substantially parallel to the front face 13a thereof. As shown in
FIG. 5, for example, each lighting device 1 can be fixed to a rear
side face of the upper shield wall 14b with a fixture 16 such as an
attachment bracket.
[0016] As shown in FIG. 2, the illumination light L emitted from
the lighting device 1 is projected from the front and above the
back wall 13 toward the front face 13a of the back wall 13, and is
made incident obliquely on the front face 13a of the back wall 13.
Part of the illumination light L may be projected on the upper face
11a of the display table 11. As shown in FIG. 1, the illumination
light L is projected on substantially the entire region of the
front face 13a of the back wall 13. Here, the region of the front
face 13a of the back wall 13 where the illumination light L reaches
will be referred to as an illuminated surface IR. The illumination
light L is distributed onto the illuminated surface IR in such a
way as to achieve a desired uniformity ratio. In the meantime, a
correlated color temperature of the illumination light L is
adjusted so as to be substantially uniform over almost the entire
region on the illuminated surface IR. In the case of an application
to the showcase 10, the uniformity ratio (a ratio between minimum
illuminance and maximum illuminance) is preferably equal to or
above 0.75, and a variation in correlated color temperature (a
difference between a maximum value and a minimum value of the
correlated color temperature) on the illuminated surface IR is
preferably equal to or below 100 K.
[0017] As shown in FIGS. 1 to 4, the illuminated surface IR is
segmented into a far region FR (a first region) located at a
position distant from the lighting device 1, and a near region NR
(a second region) located closer to the lighting device 1 than the
far region FR is. When the lighting device 1 is provided above the
display space S as in this embodiment, the far region FR occupies a
region on a lower side of the illuminated surface IR while the near
region NR occupies a region on an upper side of the illuminated
surface IR. Each of the far region FR and the near region NR
defines a strip region that extends in a horizontal direction
across substantially the entire length of the display space S in
front view.
[0018] As shown in FIG. 5, the lighting device 1 includes a housing
2, a light source 3, a reflector plate 4, a light shielding plate
5, and a diffuser panel 6.
[0019] The housing 2 is an elongated hollow member formed from a
thin plate made of a metal such as aluminum, a resin, or the like.
A housing space 2A formed into a trapezoidal shape on a cross
section perpendicular to a longitudinal direction of the lighting
device 1 is provided inside the housing 2. The light source 3, the
reflector plate 4, and the light shielding plate 5 are housed in
the housing space 2A. A lower surface of the housing 2 is provided
with a light projection opening 2B, which is opened downward (to
the illuminated surface IR side), and the diffuser panel 6 is
attached to the light projection opening 2B.
[0020] The light source 3 is a linear light source formed from
multiple LEDs 30 (light-emitting elements) mounted on a base plate
3a. The base plate 3a is fixed to the housing 2 while allowing its
surface mounting the multiple LEDs 30 to be directed backward
(directed to the illuminated surface IR side). A power source unit
7 formed from electronic components and the like for supplying
electric power to the LEDs 30 is provided on a rear surface side (a
front side) of the base plate 3a. The multiple LEDs 30 include
first LEDs 31 (first light-emitting elements) and second LEDs 32
(second light-emitting elements), which have correlated color
temperatures of emitted light being different from each other. The
lighting device 1 employs mixture of light emitted from the LEDs 31
and 32 as source light. As shown in FIG. 6, the first and second
LEDs 31 and 32 are arranged alternately and at regular intervals in
a line along the longitudinal direction of the lighting device 1.
In this way, light distribution control of the illumination light L
is facilitated by reducing a width of the light source 3. Note that
the number of rows of the LEDs 30 (31 and 32) is not limited to a
particular value, and it is possible to provide the LEDs 30 in two
or more rows within a range not to complicate the light
distribution control too much.
[0021] Meanwhile, the lighting device 1 includes a control unit 9
(see FIG. 6), which controls light outputs from the first and
second LEDs 31 and 32. The control unit 9 includes the power source
unit 7, and an output control unit 8 which controls the light
outputs from the respective LEDs 31 and 32. The output control unit
8 can be realized by a microcomputer, a processor, a dedicated
circuit, and the like. The output control unit 8 may include a
central processing unit (CPU), a memory (such as a non-volatile
memory), and the like. A program for realizing functions of the
output control unit 8 is stored in the memory. The program may be
recorded in the memory in advance. Alternatively, the program may
be provided by being recorded in a recording medium (such as a
memory card) or provided via an electrical communication line (such
as the Internet). The control unit 9 causes the output control unit
8 to adjust a light output ratio between the LEDs 31 and 32,
thereby making the correlated color temperature of the mixed light
emitted from the light source 3 variable in a range from 3000 K to
5000 K, for example.
[0022] The reflector plate 4 is disposed at a position closer to
the illuminated surface IR than is the light source 3 in such a way
as to cover the upper and back parts of the light source 3, and is
thus fixed to the housing 2. A lower end portion of the reflector
plate 4 is opened downward to form the light projection opening 2B.
The reflector plate 4 includes a specular reflection surface R1 (a
first reflection surface) located on the surface on the light
source 3 side. The specular reflection surface R1 extends in the
longitudinal direction of the lighting device 1 (a direction of
extension of the light source 3), and has a substantially parabolic
curved shape in terms of a cross section perpendicular to the
longitudinal direction of the lighting device 1. The reflector
plate 4 can be formed from a metal such as aluminum and stainless
steel, a resin, or the like. The specular reflection surface R1 can
be formed by subjecting the surface on the light source 3 side of
the reflector plate 4 to mirror finishing, or by coating or
vapor-depositing a reflective material thereon.
[0023] As shown in FIGS. 3 and 5, the specular reflection surface
R1 performs specular reflection of the source light and projects
first light L1 onto the far region FR and the near region NR
through the diffuser panel 6. The first light L1 projected on the
far region FR and the first light L1 projected on the near region
NR may cause a difference in correlated color temperature
(hereinafter referred as "uneven color temperatures"), which is
attributed to variations in light distribution characteristics,
optical axis deviations, displacements of mounting positions, and
the like among the LEDs 31 and 32, for example. The uneven color
temperatures cause color unevenness on the illuminated surface IR.
In this embodiment, the correlated color temperature of the first
light L1 projected on the far region FR is set lower than the
correlated color temperature of the first light L1 projected on the
near region NR. Here, the correlated color temperature of the first
light L1 projected on each of the far region FR and the near region
NR can be measured, for example, by covering an auxiliary
reflection surface R2 to be described later with a low-reflectance
plate subjected to a blackening surface treatment and the like, or
by replacing the light shielding plate 5 with this plate and the
like.
[0024] The light shielding plate 5 is disposed between the light
source 3 and the diffuser panel 6, and is fixed to the housing 2.
The light shielding plate 5 is formed from a thin plate of a metal,
a resin, and the like, and is bent into an L-shape on the cross
section perpendicular to the longitudinal direction of the lighting
device 1. The light shielding plate 5 includes a base portion 5a
and a light shielding portion 5b. The base portion 5a is fixed to
the housing 2 while extending substantially parallel to the base
plate 3a at a position below the light source 3. The light
shielding portion 5b is erected on an upper end of the base portion
5a toward the reflector plate 4, and is configured to suppress the
projection of the source light on the far region FR and the near
region NR without being reflected from the specular reflection
surface R1 (i.e., to prevent direct incidence of the source light
on the diffuser panel 6 through the light projection opening
2B).
[0025] The light shielding plate 5 also functions as an auxiliary
reflector plate. A surface of the light shielding portion 5b on the
opposite side from the light source 3 and a surface of the base
portion 5a on the specular reflection surface R1 side collectively
constitute the auxiliary reflection surface R2 (a second reflection
surface), which extends in the longitudinal direction of the
lighting device 1 (the direction of extension of the light source
3). The auxiliary reflection surface R2 is provided in the housing
2 at a position opposed to the near region NR through the diffuser
panel 6. As shown in FIGS. 4 and 5, the auxiliary reflection
surface R2 reflects secondary and higher-order reflection light of
the source light (which may contain primary and higher-order
reflection light of the first light L1) inside the housing 2, and
projects second light L2 on the near region NR. In other words,
mixed light of the first light L1 and the second light L2 is
projected on the near region NR.
[0026] The auxiliary reflection surface R2 is tinted in a
prescribed color. For this reason, a correlated color temperature
of the second light L2 is different from the correlated color
temperature of the first light L1. The prescribed color is selected
such that an absolute value of the difference in correlated color
temperature between the mixed light projected on the near region NR
(a hatched portion in FIG. 2) and the first light L1 projected on
the far region FR is smaller than the magnitude of the
above-mentioned uneven color temperatures of the first light L1. In
other words, the lighting device 1 generates the light (the second
light L2) to reduce the difference in correlated color temperature
of the light projected on the two regions FR and NR on the
illuminated surface IR by tinting the second reflection surface in
the prescribed color. Here, any of well-known surface treatment
methods including painting, plating, thermal spraying, vapor
deposition, and the like may be employed as the tinting method.
[0027] In this embodiment, the color of the auxiliary reflection
surface R2 is selected such that an average value of the correlated
color temperature of the second light L2 is lower than an average
value of the correlated color temperature of the first light L1
(such that the former exhibits a warmer color than the latter). For
example, when the average value of the correlated color temperature
of the first light L1 is around 4000 K, it is possible to provide
the auxiliary reflection surface R2 with ivory matte paint (Munsell
2.5Y 9/2, which corresponds to 22-90D according to JPMA). Thus, it
is possible to set the average value of the correlated color
temperature of the second light L2 lower than the average value of
the correlated color temperature of the first light L1.
[0028] In the meantime, the color of the auxiliary reflection
surface R2 may be selected such that the average value of the
correlated color temperature of the second light L2 is lower than
the average value of the correlated color temperature of the first
light L1, when the correlated color temperature of the source light
is equal to a median value (such as 4000 K) of its variable range
(such as from 3000 K to 5000 K). Here, the "average value" of the
correlated color temperature means an average value in an
illuminated region on the illuminated surface IR. Accordingly, the
average value of the correlated color temperature of the first
light L1 represents an average value of the correlated color
temperature of the first light L1 on the entirety of the far region
FR and the near region NR. Meanwhile, the average value of the
correlated color temperature of the second light L2 represents an
average value of the correlated color temperature of the second
light L2 on the entirety of the near region NR. These average
values can be calculated, for example, as average values of the
correlated color temperatures measured at finite numbers of
representative points in the regions FR and NR, respectively. Note
that the correlated color temperature of the second light L2 can be
obtained by ng the component of the first light L1 from the mixed
light of the first light L1 and the second light L2 to be projected
on the near region NR, for example.
[0029] The diffuser panel 6 performs diffuse projection of the
first light L1, which is incident from the specular reflection
surface R1, toward the far region FR and the near region NR, and
performs diffuse projection of the second light L2, which is
incident from the auxiliary reflection surface R2, toward the near
region NR. Part of the light incident on the diffuser panel 6 is
reflected from the diffuser panel 6, and is transformed into the
secondary and higher-order reflection light in the housing 2. The
diffuser panel 6 can be formed, for example, from a transparent
panel and a diffuser sheet attached to an outer surface of the
transparent panel. For example, a matte translucent panel made of
acrylic resin can be employed as the transparent panel. For
instance, LEE 251 (manufactured by LEE Filters) can be employed as
the diffuser sheet. The uniformity ratio on the illuminated surface
IR can be improved by installing the diffuser panel 6. Here, the
diffuser panel 6 may be omitted when a sufficient uniformity ratio
can be obtained by using the specular reflection surface R1 and the
auxiliary reflection surface R2.
[0030] Operation and effect of this embodiment will be described
below.
[0031] When the light source 3 applies the first and second LEDs 31
and 32 which have the correlated color temperatures of the emitted
light being different from each other, the illumination light L may
cause uneven color temperatures, which are attributed to the
variations in light distribution characteristics, the optical axis
deviations, the displacements of mounting positions, and the like
among the LEDs 31 and 32, for example. The uneven color
temperatures cause the above-mentioned color unevenness on the
illuminated surface IR. In particular, the linear light source such
as the light source 3 has a ratio of the width (a widening rate) of
the illuminated surface IR to the width of the light source, which
is greater than that of a planar light source. Accordingly, the
uneven color temperatures tend to be amplified more. It is
difficult to sufficiently suppress the uneven color temperatures
even by use of the diffuser panel 6.
[0032] In the lighting device 1, the light (the second light L2)
designed to reduce the difference in correlated color temperature
between the light projected on the far region FR of the illuminated
surface IR and the light projected on the near region NR thereof is
generated by tinting the auxiliary reflection surface R2 in the
prescribed color, and then the generated light is projected on the
near region NR. Accordingly, it is possible to reduce the uneven
color temperatures of the light projected on the far region FR and
the near region NR by using a simple structure, and thus to
efficiently suppress the color unevenness on the illuminated
surface IR.
[0033] Meanwhile, in this embodiment, the correlated color
temperature of the first light L1 projected on the far region FR is
set lower than the correlated color temperature of the first light
L1 projected on the near region NR. On the other hand, the color of
the auxiliary reflection surface R2 is selected such that the
average value of the correlated color temperature of the second
light L2 is lower than the average value of the correlated color
temperature of the first light L1 (such that the former exhibits a
warmer color than the latter). In this way, it is possible to
reduce the uneven color temperatures more reliably and to suppress
the color unevenness on the illuminated surface IR. When the
average value of the correlated color temperature of the first
light L1 is around 4000 K, for example, it is possible to reduce
the uneven color temperatures by providing the auxiliary reflection
surface R2 with the above-mentioned ivory matte paint. Thus, the
variation in correlated color temperature, which is around 250 K in
the case of proving the auxiliary reflection surface R2 with white
paint (Munsell N9.5), for example, can be reduced down to around 70
K.
[0034] Furthermore, the correlated color temperature of the source
light is made variable in a predetermined range (such as from 3000
K to 5000 K), a median value of which is a first correlated color
temperature (such as 4000 K), by changing the light output ratio
between the first and second LEDs 31 and 32. If the source light is
set to the first correlated color temperature (the median value of
the variable range), the light output ratio between the first and
the second LEDs 31 and 32 comes close to 1, whereby the magnitude
of the uneven color temperatures of the first light L1 projected on
the far region FR and the near region NR is apt to be
maximized.
[0035] In this case, the color of the auxiliary reflection surface
R2 is selected such that the average value of the correlated color
temperature of the second light L2 is lower than the average value
of the correlated color temperature of the first light L1 when the
correlated color temperature of the source light is equal to the
first correlated color temperature. This makes it is possible to
efficiently suppress the maximum value of the uneven color
temperatures in the variable range of the correlated color
temperature.
[0036] Meanwhile, in the lighting device 1, the light shielding
plate 5 is provided with the auxiliary reflection surface R2. For
this reason, it is possible to obtain the aforementioned color
unevenness reduction effect in a space-efficient manner while
preventing the light source 3 from becoming visible directly
through the light projection opening 2B.
[0037] Moreover, the lighting device 1 is provided with the
diffuser panel 6, which is configured to perform the diffuse
projection of the incident light toward the far region FR and the
near region NR, and to reflect part of the incident light.
Accordingly, it is possible to improve the uniformity ratio on the
illuminated surface IR and to increase the amount of the second
light L2 by augmenting the secondary and higher-order reflection
light in the lighting device 1.
[0038] Next, lighting devices according to some other embodiments
of this disclosure will be described. Note that the constituents
which are the same as those in the configuration of the
aforementioned embodiment will be denoted by the same reference
numerals and explanations thereof will be omitted.
[0039] In a certain embodiment, the uneven color temperature of the
first light L1 may show a reverse trend to that in the
above-described embodiment. Specifically, the correlated color
temperature of the first light L1 projected on the far region FR
may be higher than the correlated color temperature of the first
light L1 projected on the near region NR.
[0040] In this case as well, the color of the auxiliary reflection
surface R2 is selected such that the absolute value of the
difference in correlated color temperature between the mixed light
projected on the near region NR and the first light L1 projected on
the far region FR is smaller than the magnitude of the uneven color
temperatures of the first light L1. In other words, the lighting
device 1 generates the light (the second light L2) to reduce the
difference in correlated color temperature of the light projected
on the far region FR and the near region NR on the illuminated
surface IR by tinting the second reflection surface R2 in a
prescribed color, and projects the generated light on the near
region NR. This makes it possible to reduce the uneven color
temperatures of the light projected on the far region FR and the
near region NR by using a simple structure, and thus to efficiently
suppress the color unevenness on the illuminated surface IR.
[0041] The color of the auxiliary reflection surface R2 is
preferably selected such that the average value of the correlated
color temperature of the second light L2 is higher than the average
value of the correlated color temperature of the first light L1
(such that the former exhibits a colder color than the latter).
This makes it possible to reduce the uneven color temperatures more
reliably and to suppress the color unevenness on the illuminated
surface IR. For example, when the average value of the correlated
color temperature of the first light L1 is around 4000 K, the
uneven color temperatures can be reduced by providing the auxiliary
reflection surface R2 with hisoku matte paint or very pale blue
matte paint (Munsell 5B 9/2, which corresponds to 65-90D according
to JPMA).
[0042] In another certain embodiment, the correlated color
temperature of the source light is made variable within a
predetermined range (such as from 3000 K to 5000 K). In this case,
the color of the auxiliary reflection surface R2 may be selected
such that the average value of the correlated color temperature of
the second light L2 is higher than the average value of the
correlated color temperature of the first light L1, when the
correlated color temperature of the source light is equal to a
median value (such as 4000 K) of the variable range. Thus, it is
possible to efficiently suppress the maximum value of the uneven
color temperatures in the variable range of the correlated color
temperature.
[0043] Meanwhile, in a modified example of each of the embodiments
described above, the auxiliary reflection surface R2 may be
provided with different colors depending on positions in the
longitudinal direction of the lighting device 1. Such colors may be
changed either stepwise or gradually in the longitudinal direction
of the lighting device 1. In this way, when the uneven color
temperatures of the first light L1 vary depending on the positions
in the longitudinal direction of the lighting device 1, it is
possible to generate the second light L2 in an optimal correlated
color temperature so as to correspond to the positions in the
longitudinal direction.
[0044] In another modified example of each of the embodiments
described above, the auxiliary reflection surface R2 may be
provided with different colors depending on positions in a
direction (a width direction of the auxiliary reflection surface
R2) orthogonal to the longitudinal direction of the lighting device
1. Such colors may be changed either stepwise or gradually in the
direction orthogonal to the longitudinal direction of the lighting
device 1. This makes it possible to reduce the uneven color
temperatures of the light projected on the illuminated surface IR
at a higher accuracy.
[0045] In still another modified example of each of the embodiments
described above, a second auxiliary reflection surface may be
provided in addition to the auxiliary reflection surface R2. This
makes it possible to reduce the uneven color temperatures of the
light projected on the illuminated surface IR at an even higher
accuracy by projecting a third light different from the first light
L1 and the second light L2 on a third region different from the far
region FR and the near region NR.
[0046] While the foregoing is described as what are considered to
be the best mode and/or other examples, it is understood that
various modifications may be made therein, and that the subject
matter disclosed herein may be implemented in various forms and
examples, and that they may be applied in numerous
applications.
[0047] For example, in the above-described embodiments, the light
source 3 is formed from two types of the LEDs 31 and 32 which have
the correlated color temperatures of the emitted light being
different from each other. However, the number of types of the LEDs
30 may be three or more. Meanwhile, the light-emitting elements of
the light source 3 may be formed from other semiconductor elements
such as organic EL elements (OLEDs).
[0048] In the meantime, the lighting device 1 of each of the
above-described embodiments is installed above and in front of the
illuminated surface IR. Instead, the lighting device 1 may be
installed below and in front of the illuminated surface IR, and may
project the illumination light L from that position upward and
rearward. The lighting device 1 may be installed either on the
front left or on the front right of the illuminated surface IR, and
may project the illumination light L from there toward the center
of the illuminated surface IR. The lighting devices 1 may be
annularly disposed so as to surround the illuminated surface IR.
Alternatively, the lighting devices 1 may be arranged and installed
in two or more rows in the direction orthogonal to longitudinal
directions thereof.
[0049] Moreover, the lighting device 1 of each of the
above-described embodiments is disposed substantially parallel to
the illuminated surface IR. Instead, the lighting device 1 may be
disposed nonparallel to the illuminated surface IR. In the
meantime, the shape of the lighting device 1 is not limited to the
linear shape but may be formed into a curved shape instead.
[0050] Furthermore, the lighting device 1 of each of the
above-described embodiments is applicable not only to the lighting
of the showcase 10 but also to the lighting of an open display.
[0051] As described above, the lighting device 1 according to each
embodiment of this disclosure is disposed extending along the
illuminated surface IR, and illuminates the far region FR (the
first region) and the near region NR (the second region)
constituting the illuminated surface IR at the prescribed
correlated color temperature. The near region NR is located closer
to the lighting device 1 than the far region FR. The lighting
device 1 includes the light source 3, in which the two or more
types of the LEDs 30 (the light-emitting elements) that have
correlated color temperatures of the emitted light being different
from each other are arranged in one direction. Moreover, the
lighting device 1 includes the specular reflection surface R1 (the
first reflection surface), which reflects the source light emitted
from the light source 3, and projects the first light L1 on the far
region FR and the near region NR. Furthermore, the lighting device
1 includes the auxiliary reflection surface R2 (the second
reflection surface), which reflects the secondary and higher-order
reflection light of the source light, and projects the second light
L2 on the near region NR. The auxiliary reflection surface R2 is
tinted in the prescribed color. The absolute value of the
difference in correlated color temperature between the first light
L1 projected on the far region FR and the mixed light of the first
and second lights L1 and L2 projected on the near region NR is
smaller than the absolute value of the difference in the correlated
color temperature between the first light L1 projected on the far
region FR and the first light L1 projected on the near region
NR.
[0052] The correlated color temperature of the first light L1
projected on the far region FR is lower than the correlated color
temperature of the first light L1 projected on the near region NR,
and the average value of the correlated color temperature of the
second light L2 is smaller than the average value of the correlated
color temperature of the first light L1.
[0053] The two or more types of the LEDs 30 are formed from the
first LEDs 31 (the first light-emitting elements) and the second
LEDs 32 (the second light-emitting elements). The first LEDs 31 and
the second LEDs 32 have correlated color temperatures of the
emitted light being different from each other. The lighting device
1 includes the control unit 9, which controls the light outputs
from the first and second LEDs 31 and 32. The control unit 9
changes the light output ratio between the first and second LEDs 31
and 32, thereby making the correlated color temperature of the
source light variable in the prescribed range having its median
value at the first correlated color temperature. When the
correlated color temperature of the source light is equal to the
first correlated color temperature, the correlated color
temperature of the first light L1 projected on the far region FR is
lower than the correlated color temperature of the first light L1
projected on the near region NR, and the average value of the
correlated color temperature of the second light L2 is lower than
the average value of the correlated color temperature of the first
light L1.
[0054] In a certain embodiment, the correlated color temperature of
the first light L1 projected on the far region FR may be higher
than the correlated color temperature of the first light L1
projected on the near region NR, and the average value of the
correlated color temperature of the second light L2 may be higher
than the average value of the correlated color temperature of the
first light L1.
[0055] Moreover, in this certain embodiment, the two or more types
of the LEDs 30 are formed from the first LEDs 31 (the first
light-emitting elements) and the second LEDs 32 (the second
light-emitting elements). The first LEDs 31 and the second LEDs 32
have the correlated color temperatures of the emitted light being
different from each other. The lighting device 1 includes the
control unit 9, which controls the light outputs from the first and
second LEDs 31 and 32. The control unit 9 changes the light output
ratio between the first and second LEDs 31 and 32, thereby making
the correlated color temperature of the source light variable in
the prescribed range having its median value at the first
correlated color temperature. When the correlated color temperature
of the source light is equal to the first correlated color
temperature, the correlated color temperature of the first light L1
projected on the far region FR is higher than the correlated color
temperature of the first light L1 projected on the near region NR,
and the average value of the correlated color temperature of the
second light L2 is higher than the average value of the correlated
color temperature of the first light L1.
[0056] The lighting device 1 according to each of the
above-described embodiments may include the light shielding plate
5, which suppresses projection of the source light on the far
region FR and the near region NR without being reflected from the
specular reflection surface R1, and the light shielding plate 5 is
provided with the auxiliary reflection surface R2.
[0057] Moreover, the lighting device 1 according to each of the
above-described embodiments may include the diffuser panel 6, which
diffuses the light incident from the specular reflection surface R1
and projects the diffused light toward the far region FR and the
near region NR.
[0058] The entire content of Japanese Patent Application No.
2017-001632 (filed on Jan. 10, 2017) is incorporated herein by
reference.
* * * * *